Phantoms having reference members with microchannels and diffusion weighted imaging using same

Abstract

Apparatuses and methods for diffusion weighted imaging using phantoms are disclosed herein. An example phantom may include a reference member disposed within a housing, the reference member having a rod-like shape extending parallel to a long axis of the housing, the reference member formed from a material comprising a plurality of microchannels arranged longitudinally along at least a portion of the rod-like shape, and at least a portion of the housing may be formed to emulate a shape of a human torso.

What is claimed is: 
     
       1. An imaging phantom for diffusion-weighted magnetic resonance imaging, the imaging phantom comprising:
 a housing having a cross-sectional area varying along a long axis of the housing to emulate a shape of a human torso; 
 a first reference member disposed within the housing, the first reference member having a rod-like shape extending parallel to the long axis of the housing, the first reference member formed from a material comprising a plurality of microchannels arranged longitudinally along at least a portion of the reference member; and 
 a fill material filling a volume of the imaging phantom between the housing and the first reference member, the fill material including a plurality of sections each having a different density, wherein the first reference member extends through the plurality of sections of the fill material. 
 
     
     
       2. The imaging phantom of  claim 1 , wherein respective ones of the plurality of sections of fill material are formed from materials having different diffusion characteristics. 
     
     
       3. The imaging phantom of  claim 1 , further comprising a second reference member, the second reference member having different diffusion characteristics than the first reference member. 
     
     
       4. The imaging phantom of  claim 1 , wherein the first reference member has a diffusion characteristic that is longitudinally isotropic and radially anisotropic. 
     
     
       5. The imaging phantom of  claim 1 , wherein the first reference member is formed from a plurality of polymer fibers. 
     
     
       6. The imaging phantom of  claim 1 , wherein at least one of the plurality of sections of fill material is detachable from the imaging phantom. 
     
     
       7. The imaging phantom of  claim 1 , wherein the fill material includes at least one of aqueous solution, gels, thickeners, or expanded polymer filled with an aqueous solution. 
     
     
       8. The imaging phantom of  claim 1 , wherein the reference member is positioned closer to one side of the housing to approximately match a position of a spinal cord in the human torso; and
 wherein the fill material is distinct from the housing and is configured to mimic bone surrounding the spinal cord. 
 
     
     
       9. An apparatus comprising:
 a phantom, wherein the phantom comprises: 
 a reference member disposed along a long axis of the phantom, the reference member comprising a plurality of hollow fibers, 
 a housing, wherein the reference member is disposed within the housing, wherein the housing has a cross-sectional area varying along the long axis of the phantom to emulate a shape of a human torso, 
 a fill material filling a volume of the phantom between the housing and the reference member, the fill material including a plurality of sections each having a different density, wherein the reference member extends through the plurality of sections of the fill material, and 
 wherein the phantom is configured to be received by a magnetic resonance imaging apparatus. 
 
     
     
       10. The apparatus of  claim 9 , wherein the reference member has a direction of elongation, and the plurality of hollow fibers are aligned with the direction of elongation. 
     
     
       11. The apparatus of  claim 9 , wherein the hollow fibers comprise a polymer. 
     
     
       12. The apparatus of  claim 9 , wherein the reference member includes a liquid. 
     
     
       13. The apparatus of  claim 9 , wherein at least one of the plurality of sections of fill material is detachable from the phantom. 
     
     
       14. A method comprising:
 obtaining diffusion-weighted magnetic resonance images of a calibration phantom, wherein the calibration phantom includes at least one reference member extending a length of the calibration phantom, the at least one reference member including a plurality of microchannels, wherein the calibration phantom includes a fill material filling a volume of the calibration phantom around the at least one reference member, the fill material including a plurality of sections each having a different density, wherein the reference member extends through the plurality of sections of the fill material, wherein a cross-sectional area of the calibration phantom varies along the length of the calibration phantom to emulate a shape of a human torso; 
 determining diffusion values of the at least one reference member including the plurality of microchannels based on the diffusion-weighted magnetic resonance images; and 
 establishing a relationship between the determined diffusion values of the at least one reference member including the plurality of microchannels and modeled apparent diffusion values of the at least one member including the plurality of microchannels. 
 
     
     
       15. The apparatus of  claim 9 , wherein the plurality of sections of fill material are disposed normally to the reference member. 
     
     
       16. The apparatus of  claim 15 , wherein each of the plurality of sections of fill material have a different diffusion characteristic. 
     
     
       17. The method of  claim 14 , wherein the fill material includes at least one of aqueous solution, gels, thickeners, or expanded polymer filled with an aqueous solution. 
     
     
       18. The method of  claim 14 , wherein establishing a relationship between the determined diffusion values of the at least one reference member including the plurality of microchannels and the modeled diffusion values of the at least one member including the plurality of microchannels comprises:
 comparing the determined diffusion values of at least the one reference member including the plurality of microchannels to the modeled diffusion values of the at least one member including the plurality of microchannels; and 
 determining a statistical relationship between the determined diffusion values of the at least one reference member including the plurality of microchannels and the modeled diffusion values of the at least one member including the plurality of microchannels. 
 
     
     
       19. The method of  claim 14 , further comprising:
 obtaining diffusion-weighted images of a patient; 
 determining diffusion values of the patient based on the diffusion-weighted images of the patient; and 
 adjusting the diffusion values of the patient based on the relationship between the determined diffusion values of the at least one reference member including the plurality of microchannels and the modeled diffusion values of the at least one reference member including the plurality of microchannels. 
 
     
     
       20. The method of  claim 14 , wherein obtaining diffusion-weighted images of the calibration phantom comprises:
 transmitting a sequence of magnetic pulses through the calibration phantom; 
 measuring the magnetic response of the calibration phantom after each pulse; and 
 constructing the diffusion-weighted images of the calibration phantom based on the measured magnetic responses of the calibration phantom after each pulse. 
 
     
     
       21. The method of  claim 14 , wherein the diffusion values are apparent diffusion coefficient values. 
     
     
       22. The method of  claim 14 , further comprising:
 prior to obtaining the diffusion-weighted magnetic resonance images of the calibration phantom, replacing one of the plurality of sections of fill material with a replacement section of fill material, the replacement section of fill material having a different cross-sectional area than the one of the plurality of sections of fill material.